Lab Analysis

Question 1

What does distillation do?

Answer 1

• Separates 2 or more liquids based on boiling points

Question 2

What does simple distillation do?

Answer 2

• Separate liquids with boiling point difference equal to or over 50C

Question 3

What does fractional distillation do?

Answer 3

• Separate liquids with boiling point difference less than 50C

Question 4

How is calibration factor found?

Answer 4

• Found by performing a chemical reaction in calorimeter that releases known quantity of thermal energy + measuring the resultant temperature rise

Question 5

Infrared spectroscopy: Molecule interaction with energy source

Answer 5

• Absorbs infrared radiation

Question 6

Infrared spectroscopy: Effect on Molecule

Answer 6

• Increase in bond vibration

Question 7

Infrared spectroscopy: Information obtained from technique

Answer 7

• Functional groups

Question 8

HNMR and CNMR spectroscopy: Molecule interaction with energy source

Answer 8

• Absorption of radio waves

Question 9

HNMR and CNMR spectroscopy: Effect on Molecule

Answer 9

• Increase in nuclear spin energy level

Question 10

HNMR and CNMR spectroscopy: Information obtained from technique

Answer 10

• No. of Carbon-Hydrogen environments
• No. of Hydrogens on neighbouring Carbon

Question 11

Mass spectroscopy: Molecule interaction with energy source

Answer 11

• Collision with high energy electrons

Question 12

Infrared spectroscopy: Effect on Molecule

Answer 12

• Fragmentation of molecules

Question 13

Mass spectroscopy: Information obtained from technique

Answer 13

• Molar mass

Question 14

What is a fragment ion?

Answer 14

• A positively charged molecule fragment

Question 15

What is a fragment radical?

Answer 15

• The other molecule formed alongside the fragment ion

Question 16

What is an isotope?

Answer 16

• An atom of the same element with a different molecular mass

Question 17

What is meant by m/z value?

Answer 17

Mass to Charge Ratio

Question 18

How do you test for Carbon=Carbon bonding?

Answer 18

• Undergoes addition reaction with halogens/di-halogens, etc…
• The mixture will change colour rapidly

Question 19

How do you test for the presence of hydroxyl groups?

Answer 19

• Add heat and ACIDIFIED Dichromate/Permanganate:

~ A colour change will occur in the presence of a hydroxyl group (unless tertiary)

• Turns red litmus paper blue

Question 20

How do you test for the presence of carboxyl groups?

Answer 20

• Addition of sodium hydrogen carbonate (NaHCO3)
• Lime water tests for CO2
• Turns blue litmus paper red

Question 21

What is the mobile phase of HPLC and what are its properties?

Answer 21

• The moving phase
• Is polar
• Molecules desorb into mobile phase

Question 22

What is the stationary phase of HPLC and what are its properties?

Answer 22

• The non-moving phase
• Is non-polar
• molecules adsorb into stationary phase

Question 23

What is the use of the stationary phase of HPLC

Answer 23

• Used to slow down the movements of particles based on polarity and size to see how they separate.

Question 24

In HPLC, polar molecules…

Answer 24

…move faster because they are in the mobile phase more often
- Lower retention time for smaller, more polar molecules
- Polar mobile phase attracts molar molecules

Question 25

Which peak tells us the molar mass of the parent molecule?

Answer 25

The molecular ion peak(s)
- Yes, there can be multiple

Question 26

Explain how the molecular ion peaks in the mass spectrum relate to the molecular mass of a molecule

Answer 26

• The relative molar mass of a molecule is the weighted average of these molecular ion peak abundances.

Question 27

Explain why different frequencies of infrared radiation can be absorbed by the same molecule

Answer 27

• Due to functional groups
• Different functional groups have different bond strengths, bond lengths, and different bond vibrations when exposed to infrared radiation

Question 28

Relative peak area…

Answer 28

… indicates the number of hydrogens in a particular environment